As the present trend in tire-making technology continues toward the use of higher silica loadings in rubber compounds, there is a challenge to contain levels of environmentally released volatile organic compounds (VOC), especially alcohol, during compounding, processing, cure and storage of silica-reinforced rubbers.
In our U.S. patent application Ser. No. 11/387,569, filed Mar. 23, 2006, entitled “Compounding Silica-Reinforced Rubber With Low Volatile Organic Compound (VOC) Emission,” the entire disclosure of which is hereby incorporated by reference, we described the preparation of alkoxy-modified silsesquioxane (AMS) compounds and co-alkoxy-modified silsesquioxane (co-AMS) compounds that generate less alcohol than conventional alkoxysilane-containing silica-coupling and/or silica dispersing agents used in rubber compounding. Additionally, the decreased amount of alcohol produced when using the AMS and co-AMS compounds results in vulcanized rubber compounds having one or more improved properties such as, but not limited to, enhanced rubber reinforcement, increased polymer-filler interaction and lower compound viscosity, providing for tires having improved wet and snow traction, lower rolling resistance, increased rebound and decreased hysteresis.
In the aforementioned patent application, we described AMS and co-AMS compounds that can be made by subjecting one or more trialkoxysilanes or trichlorosilanes to hydrolysis and condensation in an aqueous alcohol solution in the presence of a hydrolysis and condensation catalyst such as, but not limited to, a strong acid (e.g., hydrochloric acid, sulfuric acid, phosphoric acid, and the like), a strong base (e.g., sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like), a strong organic acid, and a strong organic base (e.g. hindered amine bases, guanidines, and the like). The AMS or co-AMS product can be removed from the reaction mixture, such as by phase separation, filtration, and/or extraction with water and an organic solvent, and the like. The product can then be dried to remove substantially any organic solvent and water remaining in the reaction mixture.
In our above-referenced U.S. Provisional Patent Applications, we described methods for preparing amino AMS, amino/mercaptan co-AMS, and amino/blocked mercaptan co-AMS compounds, particularly for use as adhesives for improved metal adhesion and metal adhesion retention to cured rubber, and for use in rubber compounds and pneumatic tires. These compounds were also prepared with strong acid, strong organic acid, strong base and strong organic base hydrolysis and condensation catalysts.
However, when a strong liquid acid, base, organic acid or organic base is used as the hydrolysis and condensation catalyst, a potential carryover of even a small amount of the liquid catalyst in the precipitated AMS or co-AMS product can require special treatment for its removal. Therefore, an alternative method for making AMS or co-AMS products, including amino AMS and amino co-AMS products, is here presented.